Parthenium species of potential use in the improvement of guayule, Parthenium argentatum

Abstract

Guayule, Parthenium argentatum, a desert shrub indigenous to Mexico, has been used at various times in the past for the production of natural rubber. A revived interest in this plant as a rubber source has led to attempts to domesticate it and develop improved varieties. A number of other Parthenium species have been crossed with guayule, with the objective of introducing new, desirable traits such as larger plant size, disease resistance, cold tolerance and greater water use efficiency. At the University of California, fertile F1 hybrids have been produced between guayule and the following species: P. tomentosum, P. fruticosum, P. schottii, P. incanum, P. rollinsianum and P. alpinum. Most of these have been carried into the backcross and F2 generations. One other cross, with P. integrifolium, has also been achieved, but the F1 generation appears to be sterile due to differences in ploidy level of the parents.